Preformed coating for magnetizable core



June 17, 1947. F J SIGMUND ET &422592 PREFORMED COATING FOR MAGNETIZABLE CORE Filed May 24, 1943 IN V EN TOR.

BY &hi h 3.-

Patented June 17, 1947 i UNITED STATES PATENT OFFICE Frank .I Sigmund and William S. Hlavn, Cleveland, Ohio, assignors, by mesne assignments, to Sigmund Corporation, a Corporation of 'Ohio Application May 24, 1943,'Scrial No. %8,170

1 Claim.

Our invention relates in general to a pre-formed coating for a magnetizable core having a plurality of teeth and winding slots.

This application constitutes an improvement over our pending application filed April 12, 1943, Serial No. 482,'710 for Magnetizable core.

An object of our invention is the provision of a pre-formed rubber-like coating for the end portions and the teeth and winding slot portions of a magnetizable core and particularly for a magnetizable core for a dynamo-electric machine.

Another object of our invention is the provision of anchoring the pre-formed rubber-like material to the magnetizable core by means of any suitable adhesive composed either of the same rubber-like material from which the coating is formed or of different material.

Another object of our invention is the provision of applying rubber-like material between the laminations of the core and of anchoring the pre-formed rubber-like cover to the rubber like material between the laminations.

Another object of our invention is the provision of a pre-formed rubber-lke covering for the magnetizable core wherein the covering may beapplied to the core like a glove.

Other objects and a fuller understanding of our invention may be had by referring to the following description and claim taken in conjunction with the accompanying drawing, in which:

Figure 1 shows a cross-sectional View of a stator of a dynamo-electric machine having our preformed rubber-like cover applied thereto;

Figure 2 is a semi-circular portion of our preformed rubber-like cover;

Figure 3 is an enlarged view of a fragmentary portion of the laminated core showing particularly the adhesive between the pre-formed rubber-like cover and the laminations;

Figure 4 is an enlarged and fragmentary view of a portion of the lamination Construction and shows the rubber-like material between each of the laminations; and

Figure 5 shows a'mold upon which the preformed rubber-like cover may be formed.

With reference to Figure 1 of the drawing, the core u may comprise a stack of laminations !3 and end rings 12 suitably held together in any well known manner. As illustrated, the end portions !8, the teeth portions [9 and the winding slot portions 20 are covered with a pre-formed sheet of rubber-like material ll. In our invention, the rubber-like material includes a variety of substances in which the predominatng resinous Component may comprise polymers of vinyl compounds, such as vinyl chloride, vinyl acetate, vinyl acetals and alcohols, and vinylidene chloride. It may further include mixtures and copolymers of the vinyl compounds either with or without substantial amounts of plasticizers usable with these resins. Natural rubber or synthetic rubber may be employed.

We find that the compounds identified above give very good results, however, we do not want to be specically confined to these compounds as our invention contemplates the use of any rubbe'-1ike material or synthetic rubber-like compound with distinctive qualities which make that compound the most suitable for the insulation such as: (1) low water absorption, (2) high electrical resistance, (3) great resistance to Chemicals including acids, alkalies, corrosives and .gases, (4) good tensile strength, and (5) easy to apply to the magnetizable core.

The softening point of the rubber-like material should be as high as possible, thus permitting the temperature of the motor to rise to a high Value. The rubber-like plastics or their compounds have a wide range of temperature resistance and point of softening. Some begin to soften at F. or more. Other grades can be employed with a softening temperature higher than 200 F. and do not become brittle at subzero temperatures and which have high dielectric and high tensile strengths.

The pre-formed sheet of material or covering lil is arranged to fit over the end portions IS, the teeth portions !9 and the winding slot portions 20 like a glove. The pre-formed sheet of material or cover l l may be made in a shape to have radially extending hollow portions 22 to fit the teeth !9 and flat disc fianges 2l to fit the end portions !83 of the core and may be made in any suitable manner. One method of making the pre-formed sheet of material or cover ll may comprise using a mold ll having substantially duplicate dimensions as the magnetizable core portion to be covered and dipping the mold ll in a solution of the above-identified rubber-like material. The rubber-like material may be applied to the mold ll by spraying or any other suitable means. After the rubber-like material has been cured it may be removed from the mold l'l by peeling the same therefrom, which produces the item shown in'Figure 2. After the sheet of material or cover H is removed from the mold ll it may be then tested for leaks or other defects. Upon the approval of the testing of the sheet of rubber-like material ll, it may then be applied to the ends !8 of the core and the teeth [9 and the winding slots 20 like a glove. Prior to the insertion of the sheet of material or cover H upon the core, the core may be treated with a cement or adhesive means so as to anchor the cover l I to the core. The adhesive means may be made of the the nature of cement.

shown by the reference character !6 in the fragmentary and enlarged View of Figure 3.

As shown in Figures 3 and 4,' the rubber-like material is applied between the laminations l3, the rubber-like material being designated by the reference character [4. In practice, every other one of the laminations may be dipped in a rubber-like material so that when they are all stacked, the rubber-like material appears between each lamination. As an alternative, the sheet may be sprayed. The stacked core may be pressed together very tightly to squeeze out any eXcess rubber-like material, with the result that a very thin layer of rubber-like material is present between the laminations. The stacked core may be heated to set the rubber-like material between the laminations. The heating may be done either by electrical induction or by placing the stacked laminations in a suitable drying oven or the like. After the rubber-like material between the laminations is set or dry, then the pre-formed cover l I may be applied to the core as explained hereinbefore. The rubber-like material [4 be tween the laminations serve as anchoring points for the cover I I. The anchoring parts or portions are indicated by the reference character !5 in Figures' 3 and 4.

The thickness of the rubber-like coating l l depends upon the purpose for which the dynamoelectric machine is to be used. If the machine is to be merely exposed to dust, atmospheric moisture or chemically Corrosive fumes, the thickness oi the coating need not be greater than the commonly used fish paper slot sleeves, namely about n to %e of an inch thick. The thickness may be greater if complete Water-proofing is desired. In that case, the thickness may be as much as from %a to /o of an inch. To obtain a thickness of %a of an inch it may require as many as five or six dippings. For best results, the coating may be permitted to dry in air for about thirty minutes between each dipping and then after all of the dippings are made the mold ll with the coating thereabout may be dried by any suitable heating method, such for example as by heating oven or the like. The coating of the rubberlike material ll forms a water-tight coating and is somewhat fieXible and will not crack or break incident to contractions and expansions of the laminations. The coating may also be exposed to a wide range of temperatures without cracking or permitting the moisture to pass therethrough. The coating may withstand temperatures as low as substantially 50 to '70 degrees below zero and up to softening points.

After the coating H is properly anchored to the magnetizable core, the core is then ready for the insertion of the windings in the slots 20. The coating is somewlrat elastic and shock absorbent in that the windings are protected against vibration. Moreover, the coating is slightly deformable so that as the Windings are locked in position in the slots, the windings merely become slightly embedded in the coating so that there is a good contact between the windings and the coating which increases the dissipation of heat and the dielectric strength. The fact that the windings make a good contact with the covering in the slots also provides an arrangement which reduces the tendency of the'windings to vibrate as would be the case if a good firm contact were not made.

The rubber-like coating ll also protects the windings where they overlap the edge on the ends of the slots. The layers of rubber-like material between the laminations prevent capillary attraction of the moisture and keep the slot per fectly dry. In addition, the rubber-like material between the laminations provides anchoring points as indicated by the reference character !5, so that the coating within the slots are firmly anchored at these anchoring points to prevent any separation between the coating in the slots and the laminations.

As an alternative, the sheet of rubber-like cover ll may have the portions which cover the teeth 9 removed so that When the cover l| is applied to the magnetizable core the teeth IS are exposed which maintains a minimum air gap between the stator teeth and the rotor.

Besides making the rubber-like cover H by a dipping process as explained hereinbefore it may be made by electrical deposition or in any other manner.

Although we have described our invention with a certain degree of particularity, it is understood that the present disclosure has been made only by Way of example and that numerous changes in the details of Construction and the combination and arrangement of parts may be resorted to without departing from the spirit and the scope of the invention as hereinafter claimed.

We claim as our invention:

In a dynamoelectric machine having a magnetizable core of laminated sheets with a plurality of teeth and winding slots extending from one end of the core to the other, the provision of a one-piece slip-on cover for the surfaces of the ends of the core and the teeth and winding slots, said slip-on cover being stretchably -esilient to permit the cover to be stretched to slip upon the core and contract to fit snugly upon the sur.. faces of the ends and the teeth and the winding slots of the core and provide a cover for all said surfaces, and thin pliable resilient layers between the said laminated sheets, said cover being anchored to the layers between the laminated sheets.

FRANK .T. SIGMUND. WILLIAM S. HLAVIN.

REFERENCES CITED The following refcrences are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,05'7,503 Sawyer Oct. 13, 1936 2,089,583 Sigmund Aug. 10, 1937 491,'?08 Jefferson Feb. 14, 1893 1,748,381 cullin Feb. 25, 1930 2,232,812 Studer Feb. 2311941 832277 Schwarschild Oct. 2, 1906 1,548,889 Klein Oct. 4, 1925 l,909,892 Pope May 16, 1933 1,988,709 Barns Jan. 22, 1935 2,l30,921 Hansen Sept. 20, 1938 2158206 Spamel May 16, 1939 1,375,007 Kimble Apr. 19, 1921 1,678,380 Cooper July 24, 1928 FOREIGN PATENTS Number Country Date 392261 Great Britain 1933 OTHER REFEREN CES Hawkins, The Dynamo, vol. 1, 6th ed., Pitman & Sons, London, 1922. Page 328. 

